My weedeater lawnmower is 3 1/2months old and it will run for about 10 seconds and then it dies. Is it the spark plug?

Probably fuel related. Not the plug, could be trash in the carb, or water in the carb. Remove the carb fuel bowl, and clean. If you find any contamination in the fuel, remove the fuel from the tank, and lines. Then if it has a filter, replace also, then add fresh fuel.

Outlook Express 6 error 404... how do I fix it?

Umm, sorry, you may need to take the outlook express question to the computer section.